A quantum dot electroluminescent device (QLED), like an organic light emitting device (OLED), may actively emit light and has advantages of a fast response speed, wide angle of view, light weight, low power consumption and the like; meanwhile, compared with the OLED, the QLED has a higher color purity and may implement a wider color gamut when being applied to a display device. A quantum dot material may easily dissolve in a variety of solvents by changing surface ligands, and is very suitable for a low cost solution processing technology.
At present, there is a larger gap between a luminescent efficiency of the QLED and that of the OLED, wherein on the one hand, because a material of a QD (quantum dot) luminescent layer in the QLED is prepared by a solution method, the material has more defective states in itself, so as to reduce the luminescent efficiency of the material; on the other hand, in a device structure design, in order to obtain a device with a high efficiency, it is necessary to balance a carrier concentration injected in the luminescent layer. In the OLED design, since an energy level of the luminescent layer material is moderate, a variety of functional layer materials may be selected to match the energy level thereof (an energy barrier <0.3 eV), which may implement the efficient carrier injection and balance. However, in the QLED design, since the QD material has a deeper HOMO (highest occupied molecular orbital) energy level, there is a larger energy barrier (>1 eV) between a hole transmission material and the HOMO energy level of the QD material, while an electron injection hardly has the energy barrier, thereby causing a serious imbalance between the electrons and the holes, and reducing the luminescent efficiency of the device.